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    <title>Document</title>
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<script>
    function PqString (str){
        var arr = str.split('&')
        var obj ={}
        for (var i= 0;i<arr.length;i++){
            var ar = arr[i].split('=')
            obj[ar[0]]= ar[1]

        }
        return obj
    }
    var str = "username=admin&password=123456";
    var obj= PqString (str)
    console.log(obj);
</script>